Optical probe

ABSTRACT

An optical probe having simplified and optically improved means for obtaining movement of the field of view attitude and perspective. High light efficiency, optical resolution and depth of focus are provided, together with a substantial reduction in the number of optical and mechanical elements as compared to conventional visual flight simulation systems. A television camera has its field of view through a minor portion of the field of view of an extremely wide angle lens, and relative movement between the lens and the television camera provides a viewing attitude and perspective change without requiring tilting of the television camera or lens.

[45] June 20, 1972 United States Patent Horowitz ...35/l2 N 35/12 N X....35/l2 N X OPTICAL PROBE 3,367,046 2/1968 Neuberger 3,459,465 8/1969Rosin et al [72] Inventor. Donald J. Horowitz, Santa Clara, Calif.3'052753 9 l 1962 Schwm et aL [73] Assignee: Lockheed AircraftCorporation, Burbank,

Calif.

Primary Examiner-Robert W. Michell Assistant Examiner--L. R. Oremland[22] Filed: Aug. 17, 1970 ABSTRACT 21 Appl. No.: 64,224

N 35/102 An optical probe having simplified and optically improved7/00G09b 9/08 means for obtaining movement of the field of view attitude35 [12 N 102; 178/DIG 35 and perspective. High light efficiency, opticalresolution and 178/181 7.85, 792; 350/247 depth of focus are provided,together with a substantial reduction in the number of optical andmechanical elements as [52] US. Cl. [51] Int. [58] Field compared toconventional visual flight simulation systems. A television camera hasits field of view through a minor portion References Cited 7 UNITEDSTATES PATENTS of the field of view of an extremely wide angle lens, andrelative movement between the lens and the television camera provides aviewing attitude and perspective change without requiring tilting of thetelevision camera or lens.

6 Claims, 9 Drawing Figures 3,275,743 9/1966 2,481,082 9/1949Chew..........

3,076,271 2/1963 Marvin et al...

3,401,233 9/1968 Hellin gs T.V.CAMERA TRANSLATION CONT PATENTEDauxzo m2SHEET 10! 6 APZOO INVENTOR.

PATENTEnJuuzo m2 SHEET 2 BF 6 FIG 4 FIG..3

INVENTOR. DONALD J. HOROWITZ Attorney PATENTEDJUN 20 m2 SHEEI 3 0F 6INVENTOR. DONALD J. HOROWITZ Isa W7 y -fl fi fi/ Attorney SHEET 0F 6FEEDBACK POT ; GEARHEAD BALL NUT BALL T.V. CAMERA FEEDBACK POT INVENTOR.DONALD J. HOROWITZ BALL BUSHING Ill PATENTEDJUN 20 m2 SHEET 5 OF 6 I n 1.i! w. 1 02- ImDm OZEMDQ BA'EL NUT #1:

F I I l I l l l l 1 l ll INVENTOR. DONALD J. HOROWITZ Attorney 2 OPTICALPROBE The present invention pertains to an optical imaging apparatusproviding movement of the field of view attitude and perspective byrelative movement between a wide angle field of view lens and an opticalimage receiving surface which is adapted to receive only a selectedminor portion of the optical image of the wide angle lens.

The necessary three degrees of attitude movement in flight simulationsystems have been conventionally achieved by tilting the camera and/orlens system (optical probe) mechanically with respect to the terrainmodel. Such optical probes conventionally are constructed from a largenumber of moving optical elements with associated gears, bearings andother parts. Generally they sacrifice light efficiency for increaseddepth of focus. (The depth of focus problems associated with viewing aterrain model from very close but varying distances are quite critical.)The resulting low light efi'iciency requires expensive high intensitylighting with attendant cooling problems, restricts proper shadowingeffects, and limits the use of color television. The following U. S.Pat. Nos. are illustrative of the prior art in this area: B. S.Hemstree, 2,975,671, Mar. 21, 1961, and 3,071,875, Jan. 8, 1963; P. L.Fox, 3,114,979, Dec. 24, 1963; T. P. Neuberger, 3,367,046, Feb. 6, 1968;N. E. Lamb, 3,371,432, Mar. 5, 1968; A. G. Barnes, 3,401,228, Sept. 10,1968; G. M. Hellings, 3,401,233, Sept. 10, 1968; S. Rosin, et al,3,459,465, Aug. 5, 1969; and A. Schwartz, et al, 3,052,753, Sept. 4,1962. The above prior art patents illustrate the numerous differentapproaches which have been utilized in attempting to overcome thedifficult optical and mechanical problems associated with flightsimulation devices.

In contrast to the art cited above, the optical imaging apparatusdescribed herein provides a greatly simplified visual flight simulatingsystem with images of excellent fidelity requiring only minimal lightingof the terrain model and yet providing almost infinite depth of focus sothat focusing mechanisms may be eliminated altogether. A singlerelatively inexpensive commercially available lens may be utilized. Thisextremely wide angle lens (often referred to as a fish eye" lens) may beutilized directly in conjunction with properly dimensioned andpositioned light image receiving surface as described herein. The lightimage receiving surface may be provided by a conventional vidicon,plumbicon, photographic film, or a direct optical viewing surface. Acommercially available one inch vidicon television camera tube is shownin the specific embodiments described hereinbelow.

In the optical imaging apparatus described herein the three degrees oftranslational freedom (altitude and movement along both horizontal axes)may be conventionally provided by movement of the camera and lens withrespect to the terrain model. But in contrast to the complex prior artmechanisms cited above, the three degrees of attitude freedom (pitch,roll and yaw), are not provided by a complicated electromechanicalarrangement for tilting the camera and/or lens with respect to theterrain model. Rather, pitch and roll are provided by simple lateraltranslation of the lens relative to the camera in a single plane. Thismovement may be provided either mechanically or electronically. Therelative movement between the light image receiving surface and the lensmay be made electronically by movement of the raster electronically onthe face of a vidicon tube, utilizing conventional techniques describedherein in connection with FIG. 9 and exemplified by the circuits shown,for example, in U. S. Pat. Nos.: 2,490,561, 2,510,670, 2,774,964,3,081,557, 3,181,140, 3,281,822, 3,336,497, 3,336,398, 3,491,200,3,495,888, and 3,507,990. Roll may be conventionally provided byelectronically rotating the television raster or by optically rotatingthe image by a dove or pechan prism rotated in the optical path. In thepresent system any translational and/or attitude movements may be madesimultaneously and/or in any combination.

Further objects, features and advantages of the present inventionpertain to the particular arrangement and structure whereby theabovementioned aspects of the invention are attained. The invention willbe better understood by reference to the following description and tothe drawings forming a part thereof, which are substantially to scale,wherein:

FIG. 1 is a perspective view of an exemplary visual flight simulationsystem incorporating optical imaging apparatus in accordance with thepresent invention;

FIG. 2 is a simplified plan view of the exemplary optical imagingapparatus in FIG. 1 in which for clarity only the vidicon tube, thelens, and the terrain model are shown;

FIG. 3 is the same view as FIG. 2, illustrating the change in the fieldof view from FIG. 2 due to the translation of the lens with respect tothe vidicon image surface;

FIG. 4 illustrates in superposition the fields of view and opticalimages from FIGS. 2 and 3;

FIG. 5 illustrates in a detailed top view the optical imaging apparatusof FIGS. 14;

FIG. 6 is a side view of the exemplary optical imaging apparatus ofFIGS. 1-5 taken along the line of 6-6 of FIG. 5;

FIG. 7 is an end view of the optical imaging apparatus of FIGS. 1-6taken along the lines of 7-7 of FIG. 5;

FIG. 8 is a bottom view of the optical imaging apparatus of FIGS. I-7;and

FIG. 9 is an electronic block diagram (schematic) of electroniccircuitry for electronic raster rotation in the optical imagingapparatus of FIGS. l-8. Also illustrated is additional circuitry forproviding electronic horizontal and vertical movement of the raster areaposition and there by all electronic pitch and yaw as an alternative tothe electro-mechanical system illustrated in FIGS. 5-8.

Referring to the drawings, there is shown therein an exemplary opticalimaging apparatus 10 providing movement of the field of view attitudeand perspective in a visual flight simulating system. Referring inparticular to FIG. 1, it may be seen that the optical imaging apparatus10, which includes a television camera 17, is moveable with respect to aterrain model 12 on a moveable camera mount 14 which moves along a track16. The television camera 17 provides an electronic image of the terrainmodel 12 which is electronically transmitted to a television projector20 where it is projected on a projection screen 18 (or CRT monitor).There it is both visually observed and controlled by a pilot 22 in aflight simulator cockpit 24. This control by the pilot 22 of the opticalimaging apparatus 10 is provided by feeding the pilot control movementback electronically through a TV camera translation control 26 to thecamera mount 14. Both the camera mount 14 and the optical imagingapparatus 10 are controlled by a computer as a function of pilot inputsand the simulated dynamics of the particular vehicle being simulated.Other than the optical imaging apparatus 10, the above other componentsof the flight simulating system may be conventional, as shown forexample in the above-cited US. Pat. No. 3,052,753. The present inventionrelates to the optical imaging apparatus 10 described in greater detailherein.

For purposes of convenience in the description of FIGS. 2-8 herein, itwill be assumed that the optical axis of the lens 32 is vertical,viewing a horizontal terrain model beneath the lens. It will beappreciated, however, that the optical imaging apparatus 10 may actuallybe operated in any orientation, including that illustrated in FIG. 1.

The basic details of the exemplary optical imaging apparatus l0 and itsmode of operation may be very clearly seen in the simplified views ofFIGS. 2-4. There is shown a conventional vidicon tube 28 having imagedupon it an angular field of view 30 (approximately of the terrain model12, through an extremely wide angle objective lens 32; i.e., the lens 32is optically interposed between the television camera 17 and the terrainmodel 12. The lens 32 itself has a full angular field of view 34 ofapproximately It may be seen that only that portion of the full angularfield of view 34 of the lens 32 which is intercepted by the light imagereceiving surface area 36 of the vidicon 28 is viewed and transmitted atany one time. By the light image receiving surface 36 is meant that partof the light sensitive surface of the vidicon 28 which is transmittingan image, i.e., being scanned by its raster, and not necessarily theentire light sensitive surface (image frame area) of the vidicon.

The lens 32 is the only lens required in the entire system, in contrastto the complex lens system of the cited art. It is a modern, extremelywide angle lens, having an angular field of view of at least 170 toprovide the necessary field of view coverage as well as sufiicientperspective distortion. This perspective distortion (exaggeration) isutilized in the present system. The light image receiving surface area26 of the vidicon 28 is located at all times in the focal plane of thelens 32, i.e., they are spaced apart by the focal distance of the lens32. The lens 32 is selected so that its image area 35 (at its focalplane) is a selected ratio of the light image receiving surface area 36.This ratio is approximately 4 to 1 in area (2 to l in dimensions). Ithas been found that available 35 millimeter camera lenses with a greaterthan 170 field of view are directly compatible in the present apparatus(without masking) with commercially available 1 inch vidicons, whichhave approximately 16 mm size image frame area. This 16 mm size image isone-fourth the area of the lens 35 mm image area size and thereforemeets the desired 4 to 1 ratio. A specific example of an appropriatelens is the fish eye Nikkor lens for 35 mm cameras which has anf5.6 anda 7.5 mm focal length. A matching appropriate specific vidicon camera isthe Fairchild TCS 950, which has a standard one inch vidicon. Thiscapability for the use of commercially available components is obviouslyhighly advantageous.

Referring again to FIGS. 2-4, it can be clearly seen that the field ofview is pitched-up" simply by lateral movement of the lens 32 withrespect to the vidicon 28. In the straight down view of FIG. 2 theoptical axis of the lens 32 is perpendicular the center of the lightimage receiving surface area 36 of the vidicon 28. Thus the vidicon 28views only a central minor portion of the full image area 35 of the lens32 (approximately one-quarter the area). The rest of the image of lens32 is in effect masked" at any given lens position. When the lens 32 ismoved off-center, as in FIG. 3, a different minor portion of the lensimage area 35 is viewed by the surface 36. The angular field of view ofthe vidicon through the lens 32 remains approximately 80 but is shiftedto a different portion of the 180 field of view of the lens 32. Thus itmay be seen that the lens 32 need only be driven in a linear plane intwo axes parallel to the vidicon face to produce the visual effects ofan attitude change on two axes, and thereby provide two degrees ofattitude freedom in the resulting image. The total motion required tofully vary the image attitude is in the order of only one-half inch withthe components discussed herein. This assists in simulating high ratesof pitch and yaw change. A simple electromechanical servomechanism asshown and described in connection with FIGS. 5-8 may thus be utilized toprovide all pitch and yaw changes, and the almost infinite depth offocus and high light efiiciency of the lens may be fully utilized. Itwill be appreciated that the vidicon may be moved rather than the lens,if desired.

The field of view of the TV camera 17 may partially extend outside thefield of view of the lens 32 whenever a portion of the light imagereceiving surface area 36 moves laterally outside of the image area 35of the lens 32. (Corresponding to a pitch or yaw angle approaching thehorizon.) However, this does not present a problem. The TV camera simplysees a dark area in the area outside the image area 35 of the lens. Theflight simulation system, with this information (or the feedbackinformation of the attitude angle), can project light in this dark areafrom the TV projector 20 to simulate sky light. Such techniques areconventional, as illustrated for example in the referenced US. Pat. No.3,507,990.

Referring now particularly to FIGS. 54!, there is illustrated therein anexemplary electromechanical arrangement for achieving optical simulationof pitch and yaw in the optical imaging apparatus 10. There is shown anexemplary servomotor driven dual moving platform arrangement forproviding the desired single plane two-axis lens movement describedabove. (The components will, of course, normally be enclosed by anexternal shield, with only the lens opening exposed. For clarity herethis shield is not shown.)

As clearly seen in the side and end views (FIGS. 6 and 7) the TV camera17 with the vidicon 28 therein is mounted to a fixed platform 38. Thelight image receiving surface area 36 views the selected portion of theimage of the lens 32 (though an aperture in the fixed platform 38) asdescribed above in connection with FIGS. 2-4. Mounted underneath thefixed platform 38 for movement on one horizontal axis is an upper movingplatform 40. A lower moving platform 42 is in turn mounted beneath (andto) the upper moving platform 40 for movement on the opposite(perpendicular) horizontal axis. The lens 32 is mounted to this lowermoving platform 42, and thus is moveable on both horizontal axes byselected movements of the upper and lower moving platforms 40 and 42.

All of the disclosed exemplary components for this movement of theplatform 40 and 42 may be conventional commercially available hardwareitems and accordingly need not be described in detail herein. The uppermoving platform 40 here is driven by an upper servomotor 44 through afirst bevel gear set 46. The lower moving platform 42 is separatelydriven by a lower servomotor 48 through a second bevel gear set 50. Bothservomotors include integral gearheads and feedback pots (or otherfeedback devices.) The upper servomotor 44 is mounted on the fixedplatform 38 while the lower servomotor 48 is mounted on (and moves with)the upper moving platform 42. As may be seen in the top view of FIG. 5,clearance is provided in the fixed platform 38 for the movement of thelower servomotor 48. Conventional feedback arrangements may be providedthrough feedback potentiometers associated with the servomotors (asshown) for connection through the TV camera translation control 26 withthe pilot controls in the flight simulator. The mounting of the movingplatforms 40 and 42 here is by the cylindrical rods shown at oppositesides thereof. The platforms slide on the ball bushings over these rodsand are positioned by the ball nut on each platform engaging threads onthe rods. One rod for each platform is rotated by its respectiveservomotor through a bevel gear set to drive the platform. Thisarrangement is, of course, merely exemplary, as numerous otherelectromechanical arrangements may be utilized to achieve the samedesired limited two axis single plane movement of the lens 32 withrespect to the TV camera 17.

It will be noted that the lens 32 outer glass is the lowermost extremeextension of the optical imaging apparatus 10. Le, there is no part ofthe mechanism which extends beyond the lens 32. This is advantageous inthat the lens can be moved as closely as desired to the terrain modelwithout interference.

Referring now to FIG. 9, there is shown therein a generally conventionalelectronic technique, using conventional circuit components, forproviding roll, i.e., image rotation about the axis of the lens 32 andthe TV camera 17. (It will be appreciated, as previously discussed, thatother conventional optical means for image rotation may be provided.) Inthe circuit of FIG. 9 the conventional horizontal and verticaldeflection signals for the TV camera 17 are applied as shown, and areused to conventionally provide a raster square in the vidicon 28 throughdeflection amplifiers and the TV deflection coils as shown. Thesesignals are combined with the output of a conventional voltagecontrolled sine/cosine generator 52 in voltage multipliers toelectronically rotate the raster. This is a standard electronictechnique for rotation of the raster.

The additional circuits 54 and 56 which may be switched into the circuitof FIG. 9 at points A and B provide an additional function. They providean adjustable superimposed DC offset bias voltage for moving theposition of the entire raster square electronically within the vidicon.This circuitry may be used where it is desired to have an all electronicoptical imaging apparatus which does not require any mechanical lensmovement, i.e., the electromechanical lens movement of FIGS. 5-8 iseliminated and replaced by this circuitry. Pitch and roll are providedin this manner electronically by moving the light imaging receivingsurface 36 in the vidicon 28 rather than by moving the lens 32. Theraster square is electronically shifted in position within the imagingtube by the offset voltage provided at points A and B by the circuits 54and 56. This provides the necessary relative movement between the lightimage receiving surface area 36 and the lens 32. This, of course,requires a larger vidicon tube since the raster area can occupy only aportion of the vidicon image surface (frame area) at any given moment.However, since the total motion required is small, this does not presentany particular problem.

In conclusion, it may be seen that there has been described herein anovel and approved imaging apparatus having numerous advantages in bothstructure and operation. The exemplary embodiments described herein arepresently considered to be preferred; however, it is contemplated thatfurther variations and modifications within the purview of those skilledin the art can be made herein. The following claims are intended tocover all such variations and modifications as fall within the truespirit and scope of the invention.

What is claimed is:

1. In a visual flight simulating system wherein a terrain model isvariably viewed by a television camera and wherein the image of saidterrain model received by an imaging surface in said television camerais fed to and projected in a flight simulator and wherein the flightsimulator contains means for feedback signals representative of desiredchanges in attitude of the view from said television camera of saidterrain model, the improvement comprising:

an extremely wide angle field of view lens optically interposed betweensaid television camera and said terrain model;

said television camera having an angular field of view through said lensof said terrain model limited to only a portion of the wide angle fieldof view of said lens;

and servo means controlled by said feedback signals from said flightsimulator for moving said lens relative to said television camera in aplane substantially parallel to said imaging surface of said televisioncamera to make a viewing attitude and perspective change of said terrainmodel without tilting said television camera or lens with respect tosaid terrain model.

2. The visual flight simulating system of claim 1 wherein said lens hasan angular field of view of approximately 180 and said television camerahas an angular field of view through said lens of approximately 80.

3. In a visual flight simulator wherein a terrain model is variablyviewed by a light image receiving means, and wherein the image of saidterrain model is received by a light image receiving surface in saidlight image receiving means and projected in the flight simulator andwherein the flight simulator contains means for making desired changesin attitude of the view from said light image receiving means of saidterrain model, the improvement in optical imaging apparatus providingmovement of the field of view attitude and perspective comprising:

a lens having en extremely wide angle field of view about an opticalaxis;

light imaging receiving means for receiving an image of a selectedviewing area on a light image receiving surface therein, said lightimage receiving means having an effective angular field of viewextending through said wide angle field of view lens;

said lens being optically interposed between said light image receivingmeans and said terrain model;

said effective angular field of view of said light image receiv- 10 ingmeans through said wide angle field of view lens being limited to only aselected minor angular segment of said wide angle field of view;

and means for relative movement between said light image receivingsurface and said wide angle field of view lens transversely of saidoptical axis of said wide angle field of view lens to make a viewingattitude and perspective change at said light image receiving surfacewithout tiltin said light image receiving means.

4. e optical imaging apparatus of claim 3 wherein said light imagereceiving means is a television camera;

and wherein said wide angle field of view lens is optically mounted infront of said light image receiving surface of said television cameraand focuses an image in the plane of said light image receiving surfacewith an area substantially greater than the area of said light imagereceiving surface.

5. In a visual flight simulator wherein a terrain model is variablyviewed by a light image receiving means, and wherein the image of saidterrain model is received by a light image receiving surface in saidlight image receiving means and wherein the flight simulator containsmeans for making desired changes in attitude of the view from said lightimage receiving means of said terrain model, the improvement in opticalimaging apparatus providing movement of the field of view attitude andperspective comprising:

a lens having an extremely wide angle field of view about an opticalaxis and focusing an optical image of a given area of said wide anglefield of view at an image plane;

television means having an angular field of view through 0 said lens;

said television means having a light image receiving surface areapositioned at said image plane of said lens but occupying only aselected minor portion of said given area of said optical image of saidlens for receiving only a selected minor segment of said wide anglefield of view of said lens;

and means for moving said selected minor segment of said wide anglefield of view by relative movement between said light image receivingsurface area of said television means and said lens transversely of saidoptical axis of said lens to make a viewing attitude and perspectivechange at said light image receiving surface.

6. The optical apparatus of claim 5 wherein said light image receivingsurface area of said television means is approximate- 5 5 ly one-fourthsaid given area of said optical image of said lens.

1. In a visual flight simulating system wherein a terrain model isvariably viewed by a television camera and wherein the image of saidterrain model received by an imaging surface in said television camerais fed to and projected in a flight simulator and wherein the flightsimulator contains means for feedback signals representative of desiredchanges in attitude of the view from said television camera of saidterrain model, the improvement comprising: an extremely wide angle fieldof view lens optically interposed between said television camera andsaid terrain model; said television camera having an angular field ofview through said lens of said terrain model limited to only a portionof the wide angle field of view of said lens; and servo means controlledby said feedback signals from said flight simulator for moving said lensrelative to said television camera in a plane substantially parallel tosaid imaging surface of said television camera to make a viewingattitude and perspective change of said terrain model without tiltingsaid television camera or lens with respect to said terrain model. 2.The visual flight simulating system of claim 1 wherein said lens has anangular field of view of approximately 180* and said television camerahas an angular field of view through said lens of approximately 80*. 3.In a visual flight simulator wherein a terrain model is variably viewedby a light image receiving means, and wherein the image of said terrainmodel is received by a light image receiving surface in said light imagereceiving means and projected in the flight simulator and wherein theflight simulator contains means for making desired changes in attitudeof the view from said light image receiving means of said terrain model,the improvement in optical imaging apparatus providing movement of thefield of view attitude and perspective comprising: a lens having enextremely wide angle field of view about an optical axis; light imagingreceiving means for receiving an image of a selected viewing area on alight image receiving surface therein, said light image receiving meanshaving an effective angular field of view extending through said wideangle field of view lens; said lens being optically interposed betweensaid light image receiving means and said terrain model; said effectiveangular field of view of said light image receiving means through saidwide angle field of view lens being limited to only a selected minorangular segment of said wide angle field of view; and means for relativemovement between said light image receiving surface and said wide anglefield of view lens transversely of said optical axis of said wide anglefield of view lens to make a viewing attitude and perspective change atsaid light image receiving surface without tilting said light imagereceiving means.
 4. The optical imaging apparatus of claim 3 whereinsaid light image receiving means is a television camera; and whereinsaid wide angle field of view lens is optically mounted in front of saidlight image receiving surface of said television camera and focuses animage in the plane of said light image receiving surface with an areasubstantially greater than the area of said light image receivingsurface.
 5. In a visual flight simulator wherein a terrain model isvariably viewed by a light image receiving means, and wherein the imageof said terrain model is received by a light image receiving surface insaid light image receiving means and wherein the flight simulatorcontains means for making desired changes in attitude of the view fromsaid light image receiving means of said terrain model, the improvementin optical imaging apparatus providing movement of the field Of viewattitude and perspective comprising: a lens having an extremely wideangle field of view about an optical axis and focusing an optical imageof a given area of said wide angle field of view at an image plane;television means having an angular field of view through said lens; saidtelevision means having a light image receiving surface area positionedat said image plane of said lens but occupying only a selected minorportion of said given area of said optical image of said lens forreceiving only a selected minor segment of said wide angle field of viewof said lens; and means for moving said selected minor segment of saidwide angle field of view by relative movement between said light imagereceiving surface area of said television means and said lenstransversely of said optical axis of said lens to make a viewingattitude and perspective change at said light image receiving surface.6. The optical apparatus of claim 5 wherein said light image receivingsurface area of said television means is approximately one-fourth saidgiven area of said optical image of said lens.